The present invention concerns the technical sector of the packaging of tires which are not mounted on rims, also referred to as tire covers, with a view to transporting or storing the tires.
The incessant search for gains in productivity, coupled with a constant desire to improve the working conditions of operators in this sector, has lead the various players in the industrial sector concerned to optimize the logistic chain by acting on the storage conditions in industrial warehouses, the transport, the loading and unloading operations and on the production of easily identifiable and movable batches in line with the delivery requirements or the requirements for optimization of the storage areas. These optimizations must also not be prejudicial to the integrity of the tires.
A first solution consists of using specially sized pallets for being able to receive covers of varied dimensions and diameters. By way of example, a pallet commonly used in storage warehouses is described in the application U.S. Pat. No. 5,259,325, in which the covers (unmounted tires) are stored in a stack or in a roll. Pallets of this type have the advantage of constituting homogenous batches of covers, of being able to be disposed on top of each other over great heights, of being able to be manipulated by mechanical means of the fork lift truck type, and of offering good protection for the covers against external attacks. They are, on the other hand, less adapted to transport, in particular over long distances, because of the small number of tires which they contain having regard to their bulk, and the management of the returns of empty pallets.
For transporting over long distances, it will be sought to make the largest number of covers enter a given volume, which may equally well be a lorry trailer, a maritime container, or a railway wagon.
Another solution commonly used consists of disposing the covers on top of each other with a particular arrangement known as a “fish bone” and putting the volume thus formed under compression so as to optimize loading. These methods are described, by way of example, in the patent U.S. Pat. No. 5,092,106. Very effective for optimizing the volume to be loaded, they do, nevertheless, have the drawback of having to be produced partly manually, in particular during unloading operations, which is a limiting factor from the ergonomic point of view because of the size and weight of the covers which it is possible to manipulate. In addition, this solution proves to be particularly inefficient in a storage warehouse because of the difficulty in handling and moving the batches thus produced, because it imposes a break in packaging in the logistic chain upstream and downstream of the transport operation, and because it is liable to cause mixing, should several sizes of cover be packaged in the same load. Finally, it is not without effect on the integrity of the tires because of the deformations which the latter may undergo.
To this end it is remarkable to find that each of the solutions mentioned above represents an optimum solution for a particular field, such as storage or transport, but rarely does the same technical solution prove to be advantageous over the entire logistic chain. This results in introducing addition handlings, which partly ruin the gains achieved by the choice of the solution most adapted to a particular point in the said chain.
This is the reason why intermediate solutions have been developed for the purpose of finding an overall optimum. One of these solutions consists of packaging the envelopes in stacks, consisting in general of around ten covers disposed on top of each other so as to form a cylinder with a vertical axis whose external surface is formed substantially by the treads of each of the covers.
This solution has the advantage of forming homogeneous handling batches which can easily be manipulated using adapted means. It thereby affords an advantageous compromise for optimizing the logistic chain over all the operations in the logistic chain, such as warehousing, the loading and unloading operations, and also transport, particularly for large covers which are difficult to manipulate manually, and proves particularly well adapted when the transport is carried out in several stages.
Once the stack is formed, the covers in the stack can be fixed together by a tie or strap as proposed in British Patent GB 166,747 or U.S. Pat. No. 1,507,376, by a shrink film as described in the U.S. Pat. No. 4,858,415 or remain under the sole action of their own weight.
Industrial machines, of the type proposed by the U.S. Pat. No. 3,955,491, have been developed to form stacks automatically in a first step, and then secondly disposing one or more holding straps.
According to the size of the covers, it is possible to dispose one or more stacks side by side on a flat pallet, generally non-recoverable, so as to optimize the size of the handling batches, or to treat the stack independently.
However, the optimization of these solutions is partly related to the number of covers which it is possible to join together within the same stack and consequently the maximum height of the stack.
In particular, it may prove particularly advantageous to produce stacks whose height corresponds to the height of the volume used for transport, and the increase in height of the trailers used in road transport results in wishing to use stacks of great height. “Great height” means heights which may commonly range up to 3 m, or even more, in certain particular cases.
It is found that these stacks are particularly tricky to manipulate in the absence of means for fixing together the covers which make them up, because of the risk of possible falling of one or more covers during handling. Moreover, it is also found that, under the action of their own weight or under the action of the tension of the straps, these stacks have an annoying tendency to deform and to exhibit a vertical projection of their centre of gravity which is very off centre with respect to the centre of their support base, consisting in this case of the contact of the first tire in the stack with the ground, and then leading to an instability of the stack and a high and unacceptable risk of falling over.
The object of the invention is to reduce these drawbacks.